A couple of weeks back I had to write a solution for a client to track the referrer search engine from where the user came to his sites contact page, without using Google Analytics. If a user was to fill the contact form on the website, the referring search engine name and the keyword for which it was refereed was to be emailed along with the contact information. The following is a solution for the same.

The code itself is pretty simple - it checks the $_SERVER['HTTP_REFERER'] and, based on an array of search engine types, looks for a certain "query" keyname in the URL and matches what follows (with a regular expression). This can be useful for not only determining what sort of audience is visiting your site, but could also be used to present a custom message to visitors from certain search engines (or, more complicated, to show different content based on search terms).